Production of antiknock gasoline



March 2, 1937. FlTcH, JR 2,072,745

PRODUCTION OF ANTIKNOCK GASOLINE Filed Oct. 8, 1954 1 /FIXED GAS INV EN TOR.

LOUIS H. FlTCl-LJR.

A TTORNEYS.

Patented Mar. 2, 1937.

PATENT OFFICE rnonnc'non or aNrmNoeK ossonmfn Louis, E. Fitch, Jn, Bartlesville, Okla"; The First National in Bartlesville, a national banking corporation, atrator of said Louis B.

Fitch, d

eceased, assignor to Phillips Petroleum Company, a corporation of Delaware Application October s, 1934, Serial No. 547,459

3 Claims.

This invention relates to the pyrolysis of volatile hydrocarbons to produce therefrom motor fuels of high antiknock value.

' It is well known that normally gaseous hydrocarbons other than methane, when cracked at any pressure under suitable conditions of time and temperature, will yield liquid hydrocarbons partly of the motor fuel boiling range. Processes for accomplishing this purpose are normally classified as high or low pressure processes, though no sharp dividing line as to pressure may be said to mst. In general, the low pressure processes are characterized by the formation of liquid hydrocarbons primarily of the aromatic series, and the high pressure processes by the formation of liquid hydrocarbons of other series. My invention comprises a process wherein intar-related high and low pressure cracking steps are used to convert hydrocarbons of a boiling range not substantially higher than that of gasoline into a superior anti-knock motor fuel, using therefor simple and inexpensive apparatus, and producing as byproducts in substantial quantities only the fixed gases, methane and hydrogen.

More specifically, it comprises a process in which the liquids attained from a high pressure cracking process are used to supply charging stock to a low pressureprocess, and simultaneously to bonsai from two four carbon atoms per mole- 50 scrub aromatic hydrocarbons and recycle stock fromthe gases effluent from the low pressure process, with the production of a motor fuel of high anti-knock value.

The operation of my process will be evident from'the following description, taken in conjunction with the accompanying drawing, ofwhich Figure 1 is a diagrammatic view of a plant suitable for carrying out my process. In this drawing, l is a tubular heater, or heater and reaction chamber, designed for operation at pressures up to 1000 pounds per square inch or more, discharging through the pressure reduction valve 2 and the coolingcoil 3 into the high prssure fractionator l. "From this fractionator are drawn oif fixed gas and normally liquid hydrocarbons, at the top and bottom respectively. In addition, above the point of entry of the gases and liquid from the cooler: 3, there is withdrawn a side stream 5, comprising principally normally gaseous hydrocarcule, and this side stream passes through the valve 6 into the low pressure cracking unit I, said low pressure unit being either a tube coil or a The cracked tube coil and reaction chamber. gases from this low pressure unit then pass through the cooler8 and the compressor 8 back into the fractionator t, entering therein at a. point substantially below the point of withdrawal of the side stream 5. The usual devices for refluxing and reboiling will be used with the fractionator, but are not shown in the drawing for the sake of simplicity. For most efiioient operation, some measure of refrigeration at the top of the column l will be provided.

Many slightmodifications of this apparatus will immediately be evident to one skilled in the art. 10

For example, the tube coils of the high and low pressure units may be incorporated in the same furnace setting, and a diagram of a furnace so constructed is shown in Fig. 2, in which A is the low pressure, high temperature cracking coil, ex-

posed to the highest temperature in the radiant section of the furnace, and B is the high pressure coil, heated by the combustion gases in a convection section of the furnace, the temperature of the coil 13 being adjusted independently of A by the use of dampers.

Heat exchangers may also be employed where economy dictates, but are not claimed as any part of my invention. I may charge to my process any hydrocarbon liquid (except methane) which does not boil substantially above the boiling rangeof gasoline. Specifically, I may charge butane, natural or oil refinery gas fractions substantially free from methane, or straight run gasoline to be reformed A vapor recovery plant fraction consisting principally of butane and butylene in about equal proportions is charged to the high pressure still I, and cracked or polymerized at a pressure of 2000 pounds per square inch and a temperature of 870 F. The cracked products, which will contain most of the butane in the charging stock, are run into the fractionator 6-, operating at 325 pounds per square inch, with a low temperature at the column top. Fixed gases, such as methane, are liberated from the top of the fractionator and the unchanged butane and other normally gaseous 1 hydrocarbons are removed as a side stream, and cracked in the low pressure unit 1, at a temperature of about 1400 F. or 1500 F. and a pressure of is principally of the gasoline boiling range, and

10 contains 20-40 percent of aromatic hydrocarbons. It may be treated with suitable treating agents, and distilled to yield a stable gasoline of very high antiknock value.

Example 2 Straight run gasoline is charged to the high pressure unit I at a pressure of 1000 pounds per square inch, and cracked at a temperature of 950 F. The products are injected into the fractionator,

20 and the side stream from the fractionator is cracked as in the previous example. The effluent vapors from the low pressure cracking coil are cooled by the injection of cold butane through the valve H, and compressed and injected into the 25 iractionator as in the previous example. The yield obtained is approximately equal to the volume of straight run gasoline charged, but the antiknock value has been appreciably increased.

30 Example 3 Butane is charged to the high pressure coil and cracked at 3000 pounds per square inch pressure and a temperature of 1030 F.- The products of the reaction are all discharged into the frac- 35 tionator 4, operating at a pressure of 300 pounds in the first cracking stage be greater than that maintained in the fractionator, and the pressure in the second stage on the order of, or lower than 50 that maintained in the fractionator. 'It is evident,-

of course, that the insertion of the pump 9 in the line of Figure 1 of the attached drawing in place of its present position, would not constitute a departure from the spirit of my invention.

What I claim is:

l. A hydrocarbon conversion process which comprises subjecting a stream of light aliphatic hydrocarbons, substantially all of which boil below the maximum boiling point of gasoline and 60 above the boiling point of methane, to conversion conditions at high temperature and relatively high superatmospheric pressure,'passing all the products of said conversion to a separating zone maintained under a pressure relatively high but 65 lower than that used in the aforesaid conversion,

separating in said zone fixed gas, gasoline and' heavier liquids, and a fraction intermediate between said gas and gasoline, discharging the fixed gas from the process, withdrawing said intermea diate fraction and subjecting it to conversion conditions wherein the temperature is relatively high v and the pressure relatively low and wherein these I conditions are maintained for a time suificient to produce principally fixed gases and aromatic hydrocarbons, cooling the products of this latter conversion and increasing the pressure thereon and discharging them into the said separating zone at a point substantially below the point of withdrawal of the aforesaid intermediate fraction, separating the products of this latter conversion into fractions similar to those of the former conversion and discharging the combined fractions from said separating zone.

2. A hydrocarbon conversion process which comprises subjecting a stream of light aliphatic hydrocarbons, substantially all of which boil be- I low the maximum boiling point of gasoline and above the boiling point of methane, to conversion conditions at high temperature and relatively high super-atmospheric pressure, passing the products of said conversion to a separating zone, separating in said zone a fraction consisting principally of gasoline and heavier liquids and a fraction consisting principally of hydrocarbons containing from two to four carbon atoms in' the molecule, subjecting said last-mentioned fraction to conversion conditions wherein the temperature is relatively high and the pressure relatively low and wherein these conditions are maintained for a time sufiicient to produce aromatic hydrocarbons, cooling the products of this latter conversion'and increasing the pressure thereon and discharging them into the said separating zone at a point below the point of withdrawal of the fraction consisting principally of hydrocarbons containing from two to four carbon atoms in the molecule, separating the products of this latter conversion into fractions similar to those of the former conversion and discharging the combined fractions from said separating zone.

3. A hydrocarbon conversion process which comprises subjecting a stream of light aliphatic hydrocarbons, substantially all of which boil below the maximum boiling point of gasoline and above the boiling point of methane, to conversion conditions at high temperature and relatively high super-atmospheric pressure, passing the products of said conversion to a separating zone,

separating in said zone a fraction consisting prin-v cipally of gasoline and heavier liquids and a fraction consisting principally of hydrocarbons containing from two to four carbon atoms in the molecule, subjecting said last-mentioned fraction to conversion conditions wherein the temperature is relatively high and the pressure relatively low and wherein these conditions are maintained for a time sumcient to produce aromatic hydrocarbons, cooling the products of this latter conversion and increasing the pressure thereon and discharging them together with additional hydrocarbon material of substantially the same boiling range into the said separating zone at a point below the point of withdrawal of the fraction consisting principally of hydrocarbons containing from two to four carbon atoms in the molecule, separating the products of this latter conversion into fractions similar to those of theformer conversion and discharging the combined fractions from said separating zone.

. LOUIS H. FITCH, JR. 7 

